In U.S. Pat. No. 4,909,017 a method is disclosed for producing a reclosable plastic bag having a zipper that extends transverse to the longitudinal or running direction of the web of the film from which the bag is formed. In accordance with the disclosed method which is illustrated in simplified form FIG. 1 of the present application, a zipper segment 10 having interlocked profiles is fed transversely across a web of bag making film 12 and one of the profiles is attached to the web. The length of the segment is equal to approximately half the width of the desired bag. At a bag making machine the web is formed into a tube by sealing the edges of the film together with seal bars 14 after which the other profile of the zipper is attached to an inner surface of the tube by seal bar 16s. The construction of bag 21 is completed by forming a cross seal 18 by seal bar 20 which also serves to sever the completed bag from the tube.
In U.S. Pat. No. 6,116,314 problems associated with attaching a zipper transverse to the running direction of a bag making film are discussed. In this patent and other relatively recently issued patents, the problems of attaching transverse direction zipper are addressed by providing the zipper profiles with extended flanges to facilitate the attachment process. In many instances, however, it is desirable to use a flangeless zipper or a zipper with limited flanges. For one thing, such zippers utilize less plastic and hence tend to be cheaper than zipper with flanges. In addition, because of their smaller size, greater lengths of flangeless or limited-flange zipper can be wound on comparably sized rolls as compared with flanged zipper which enables longer production runs.
The present invention relates to a method and apparatus for attaching zipper to film that can be used with virtually any type of zipper profiles. That is, the zipper profiles may be flanged, flangeless or anything in between. In accordance with the present invention, an apparatus for attaching discrete lengths of zipper at spaced intervals across a film has an endless belt supported between a pair of pulleys for moving a zipper segment onto a web of bag making film moving along a path off a supply roll. The zipper consists of profiles with interlocked engagement elements and is fed with one profile atop the other. The zipper segments are cut from a zipper supply and fed into a nip between the endless belt and the web top surface. After a zipper segment is deposited into position on the web, the pulleys are raised to disengage the zipper segment from being driven further by the endless belt. A sealing bar below the web is then raised into position to heat the bottom surface of the web to seal the bottom profile of the zipper to the web top surface after which the sealing bar is lowered. The web then advances and the process is repeated. The resultant bag making film with attached zipper may then be fed directly into a bag making machine or spooled for later use.